STRUCTURAL CHARACTERIZATION OF A HASSI-MESSAOUD PETROLEUM ASPHALTENE

Tensiometry, elemental analysis and proton-NMR methods are used to determine structural properties of an asphaltene from an Algerian crude oil. A surface tension measurement was conducted to evaluate themicellar critical concentration as 0.0028 wt %. This value indicates that the asphaltene studied has a lower solubility and a higher aromaticity in comparison with the data found in the literature for asphaltenes of different origins. The average molecular weight calculated from tensiometry data, appears to be smaller than those measured by vapour pressure osmometry. Information about the structural parameters of the asphaltene molecule like the average number of aromatic rings, the fraction of aromatic carbon atoms, the aromaticity factor and the ratio of aromatic / peripheral carbons were extracted from elemental analysis and proton-NMR spectroscopy data using the Speight model. These results indicate that this asphaltenehas a high aromaticity and a very large aromatic sheet diameter.